1. Technical Field
This invention relates to fluid cooled lances such as used for introducing an inert gas into molten metal for stirring the same or for injecting a stream of oxygen into molten metal for refining the same.
2. Description of the Prior Art
Prior devices of this type may be seen in U.S. Pat. Nos. 3,115,405, 3,379,428, 3,521,872, 3,751,019 and 3,898,078.
In U.S. Pat. No. 3,115,405, a typical prior art lance formed of tubular metal shapes is disclosed, the lance is intended for the introduction of oxygen into molten iron in making steel and is water cooled.
U.S. Pat. No. 3,379,428 discloses a metal lance formed of a plurality of concentric tubular elements and useful in introducing oxygen into molten iron in a metallurgical furnace. The device is water cooled.
U.S. Pat. No. 3,521,872 discloses a metal lance and utilizes an arrangement of introducing water in vapor form into the gas conveyed by the lance into the molten metal.
U.S. Pat. No. 3,751,019 discloses a fluid cooled lance formed of composite refractory and metal for introducing oxygen or other gases into or onto molten metal baths. The tubular metal portions are located within an enclosing refractory sleeve.
U.S. Pat. No. 3,898,078 discloses a metal lance having a nozzle, a portion of which is covered with a refractory material.
The present invention relates to a substantially improved air cooled refractory lance in which the principal body of the lance is formed of refractory material provided with a bore in which metal conduits are positioned and through which cooling air is introduced and removed in a manner creating a positive circulation through the substantially large hollow core of the refractory body. An additional metal conduit positioned off center of the hollow core of the refractory body forms a continuous passageway therethrough for the introduction of oxygen or other gases. The novel construction of the elongated refractory body and its relatively large bore axially thereof throughout most of its length enables air to be effectively used to cool the refractory body and contribute to its substantially longer life than has heretofore been possible with the prior art lances, many of which were water cooled as in the case of the foregoing prior art patents.